This invention relates generally to add/drop multiplexers useful in optical communication networks.
Many optical communication networks operate as wavelength division multiplexed networks wavelength channels. In such networks, a number of information containing light signals (channels), of different wavelengths, may be multiplexed over a single optical communication path. At desired points, signals of a given wavelength may be added or removed from the optical path. An add/drop multiplexer is utilized to add and/or remove a particular wavelength channel from the optical path.
Tunable add/drop networks would offer a number of operating advantages to the service provider. Existing add/drop multiplexer technologies may be combined in ways that accomplish tunability. However, such a functionality on its own may be of little use in a network because of the impact on existing data streams while the components are being tuned. What is needed is a “hitless” tunable add/drop with the ability to tune without affecting or “hitting” the existing data flows. Hitless tunability may be achieved using paired analog switches to reroute the data stream through a bypass optical circuit, thereby protecting the data flow during the switching time of the add/drop multiplexer, or by using a full crossbar switch between pairs of wavelength demultiplexers.
These existing approaches may have cost, structural, and control complexities due to the use of paired analog switches or crossbar switches. In addition, they may have cost, environmental sensitivity, and reliability issues related to the use of mechanical structures.
Thus, there is a need for a better way to provide a tunable add/drop multiplexer.